The present invention refers to an adjusting unit for an article carrier with adjustable support elements for receiving thereon articles of different sizes, in particular printed circuit boards of different sizes, with a frame means, especially one frame member of said frame means being used as a support for an article to be carried, and at least one additional supporting element which is adapted to be adjusted relative to the frame member, wherein arresting means are provided with the aid of which the supporting element can be arrested relative to the frame member, said arresting means being adapted to be releasably arrested on a guide means along which the supporting element is displaceable.
Such an adjusting unit for article carriers may be used as a separate unit within a process line for processing e.g. printed circuit boards that are carried by the article carrier. In this process line a number of further systems may be used, such as e.g. a reflow soldering systems, a curing system, a drying system, etc.
It is also possible that the adjusting unit according to the invention is integrated in one of the above-mentioned systems, such as e.g. in a reflow soldering system.
Reflow soldering systems by means of which electronic components premounted on printed circuit boards are soldered and thus electrically connected to a wiring scheme on the printed circuit board under the influence of heat are generally known in the prior art. In such reflow soldering systems, it is necessary to transport the articles, i.e. the printed circuit boards, through a comparatively long system with different zones, such as e.g. a preheating zone, a main heating zone, a cooling zone and a discharge area. The printed circuit boards are moved through these zones on an article carrier by means of a transport mechanism, e.g. a conveying chain or a link belt driven by the system.
Such a reflow soldering system is an acquisition necessitating a very high investment. Hence, it goes without saying that it is necessary that such a system is suitable for more than one specific size of printed circuit board. For treating printed circuit boards of various sizes in such a reflow soldering system, it has hitherto been common practice to replace the article carrier by an article carrier adapted to the size of the printed circuit board to be processed at the time in question. This required, on the one hand, the provision of a comparatively large supply of suitable article carriers for the respective sizes of the printed circuit boards to be processed; on the other hand, complicated and time-consuming manipulations by an operator were necessary for exchanging the article carriers upon changing from one size of printed circuit boards to a new one.
Even if stocks of many different article carriers were kept in supply, it was only possible to process standard sizes of printed circuit boards to which the article carriers were adapted. Specially manufactured printed circuit boards could not be transported through such a reflow soldering system. For solving this problem, the individual article carriers had to be modified or adapted by hand by an operator.
However, any intervention on the part of the operator in the operation of a reflow soldering system results in a drastic decrease of the efficiency of the throughput through the system, and, in connection with the high acquisition costs of a reflow soldering system, this results in a significant problem of costs.
The disadvantages outlined with respect to the reflow soldering system as set forth above are also valid for any other system for processing e.g. printed circuit boards, such as curing systems, drying systems, varnishing systems, etc.
It is, therefore, an object of the present invention to provide an adjusting unit of the type mentioned at the beginning, which makes use of an adjustable article carrier and by mean of which an adaptation of the article carrier to the size of a printed circuit board to be processed can be carried out automatically and mechanically, i.e. by machine.
To overcome the disadvantages outlined above and to solve the problem underlying the invention, the adjusting unit comprises adjustment means for adapting the adjustable supporting element of the article carrier to the size of an article to be accommodated.
The adjusting unit according to the present invention provides a mechanical, automatic adaptation of the article carriers to the article size to be processed at the time in question. Hence, the downtime of the system resulting from an intervention of an operator for adjusting the article carriers is minimised, and, simultaneously, the adaptation accuracy can be increased by means of an automatic and mechanical execution of the adjustment process.
As already mentioned the adjusting unit may be a stand-alone unit but may also be an integrated part of another system, such as e.g. a reflow soldering system.
To release the supporting element relative to the frame member, the adjustment means may be provided with delocking means which are adapted to be displaced in a direction along with the position of the supporting element.
A simple embodiment of the delocking means can be characterised in that the delocking means comprise gripper elements with the aid of which clamping plates of the arresting means of the article carrier are movable in the direction opposite to a biasing force applied to the clamping plates so as to release the clamping contact of said clamping plates with the guide means. The guide means of the article carrier may be rod-like rails along which the clamping plates may be moved.
The adjusting unit may also be provided with a vertical adjustment means for adjusting a level of a centre support of the article carrier. In such a way a complete mechanical adaptability of the article carrier with regard to the dimension of the printed circuit boards to be processed as well as with regard to the level of the centre support is automatically possible.
An example for such a vertical adjustment means are wedge-like elements by means of which a displaceable plate as part of one of the support elements may be raised or lowered.
To provide at least a support for the article carrier during its adjustment, the adjusting unit comprises supporting means for supporting frame members of the article carrier at least in adjustment position of the support elements. The supporting means may also be used for moving the article carrier to and from the adjustment position and also to move the article carrier through the adjusting unit or any system in which the adjusting unit is incorporated.
According to a simple embodiment of the supporting means, they may be formed by two parallelly spaced support rails on which outwardly extending flanges of the frame members of the article carrier are placed.
To avoid any displacement of the article carrier as long as it is adjusted to the size of the printed circuit board as an article, the adjusting unit may comprise at least one clamping means vertically movable for clamping rail and flange to affix the article carrier in its adjustment position.
It may be advantageous if the clamping means are movable along the rails such that different article carriers may be fixed by the same clamping means or such that one article carrier may be clamped at different positions.
To avoid any interference of the clamping means with e.g. the supporting elements of the article carrier, clamping means may be arranged outwardly of the support rails.
To securely clamp the article carrier in its adjustment position it may be advantageous if the clamping means comprises two spaced clamping elements which are releasably fixed to a yoke member extending essentially parallel to the support rails, which yoke member is connected to a piston of a lifting cylinder. Consequently, the vertical movement of the clamping means is realised by a vertical movement of the yoke member by actuating the lift cylinder.
To support the gripper elements in an easy way and also to move them without difficulty, the gripper elements may be pivotally or slidably supported by a vertically movable gripper body.
The gripper body may be raised and lowered in the vertical direction by a spindle or the like. Another advantageous embodiment of the invention uses a rack-and-pinion drive for movably supporting a gripper body.
As an example the gripper body may be connected to a toothed rack of the drive and the drive""s pinion may be arranged on a drive shaft of an electric motor. By actuating the electric motor, the pinion is rotated and the toothed rack is raised or lowered correspondingly together with the gripper body connected thereto.
To avoid any misalignment of the gripper element and the arresting means of the article carrier, the adjusting unit may comprise a centring means that is assigned to the delocking means for centring the supporting element of the article carrier with respect to the delocking means.
As the supporting element is bar- or plate-like, the centring means may comprise a lifting cylinder and a fork-like centring element at the top of the lifting cylinder. By the lifting cylinder the centring element may be raised and lowered, wherein the centring element seizes the supporting element by its fork-like aperture.
To avoid any interference with the clamping means, the centring means and delocking means may be arranged between the supporting rails.
As the centring means and delocking means are operated together, they may be simultaneously displaceable in longitudinal direction of the support rails.
To delock the support element at both of its ends, a pair of plate-like gripper elements and one centring element may be assigned to each support rail, i.e. to each end of the support elements of the article carrier.
To simplify the movement of delocking means and centring means a carriage may be used that is arranged between the supporting rails and that is movable in longitudinal direction of the rails with at least said centring means and said delocking means arranged on the carriage.
There are different possibilities to move the carriage, such as e.g. a spindle or the like. Another example for moving the carriage is a carriage that is fixed to an endless belt which is movable in longitudinal direction of the support rails.
To energise the different element of the delocking means, centring means, etc., such as e.g. the lift cylinders, the carriage may be connected to a chain with a plurality of chain segments through which supply lines are guided. The chain connects the carriage to a frame or body of the adjusting unit and during movement of the carriage the chain will provide a deformable or adjustable connection along which the supply lines are securely guided.